The long term objective of this proposal is to reveal the molecular mechanisms underlying the effects of lead (Pb) on the developing nervous system, effects which lead to the neurobehavioral deficits found in children with "low to moderately elevated" blood Pb levels. Pb toxicity continues to be a major health problem in the United States, affecting as much as 17.2% of all preschool age children. The nervous system is one of the most sensitive and, from a societal standpoint, most important targets of Pb toxicity. The nervous system is particularly susceptible during growth and development. In the developing neuron there is an extremely fine control of the intracellular free Ca ion concentration ([Ca2+]i) and transmembrane Ca2+ movements which appear to regulate the expression of differentiated neuronal morphology. Pb alters the [Ca2+]i and Ca2+ channel activity of neurons. These observations have led to the hypothesis that the [Ca2+]i of developing neurons may be exquisitely sensitive to perturbation by Pb and that disruption of this critical intracellular messenger uncouples the timely expression of differentiated neuronal structure from normal control mechanisms. In order to test this hypothesis, the effects of Pb on [Ca2+]i, Ca2+ fluxes and compartmentation and neurite formation will be examined in developing neurons. This study will be carried out using primary cultures of rat cortical and hippocampal neurons. {Ca2+]i and [Pb2+]i will be measured using the intracellular divalent cation indicator 5F-BAPTA and 19F NMR spectroscopy. Cellular Ca2+ fluxes and compartmentation will be measured by desaturation kinetic studies. Neurite formation will be examined to monitor the development of neuronal morphology. Pb-induced changes in cellular energy metabolism will be evaluated by measuring impact of Pb on high energy phosphate levels using 31P NMR. This study is designed to demonstrate that Pb-induced changes in [Ca2+]i can mediate the neurodevelopmental toxicity of Pb.